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High Speed Vibration


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Hi All

First track day after I bought the car in January. Great day, although I am getting a vibration from the rear at high speed. It starts at about 100mph and at its worst at 110mph.

It is not related to engine speed so assume it can only be something after the gearbox.

I am going to check the rear wheels are balanced correctly but what else should I check? Wondering if it may be prop shaft related, any way to check without removing it?

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It was a private purchase. I don’t mind having to put things right as it is the right spec car I wanted at a reasonable price.

Will check the wheels are properly balanced first. Wouldn’t bearings grumble if they are on the way out? There is no play I can feel in either rear wheel. 


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I had a similar experience with an ex academy car, which had the side impact protection removed.   The wrong number of spacing washer and a over long bolt caused the A frame to snap,  thankfully at low speed and within 100 yards of my house.

If it was my car I would check the following

1, With the handbrake on get someone to rock the car with the roll bar while you check each joint and bush of the suspension (both front and rear).  Try and feel for excess play, movement that should not be there.  If you detect any and are not sure post a youtube link here.    For example this is a dedion bush that needs replacing 

2, Check the diff bolts, and spanner check all the suspension (front and rear).  Remember even a metric car is a mix of metric and imperial sizes 

3, Check for cracks in the dedion tube especially around the rear shock mounting points, and A Frame cracks.  

4, Balance and check the tyres, they could have a flat spot from sitting to long, they could be old, cracked side walls.   Check the wear pattern for signs of the problem. 

I can't help thinking a prop shaft doesn't go out of balance without some additional factor, so short of checking the joint have been greased recently (although my 2017 prop has no grease nipples)  I would assume that's not the problem, unless a visual inspection reviles some damage.  You could also check how central your gearbox mount is to help the prop run as true as possible  (assuming its not a Mazda gearbox).  

Beyond that I would seek professional help.

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Quick update, bushes all seem ok, bolts are still all tight, A frame and DD are all in great condition.

Have dropped of the rear wheels to be checked tomorrow. Looking at the tread wear pattern it does seem that one may have a slight flat spot. Although without prompting the mechanic did ask if the prop shaft was ok when describing symptoms...

on FB someone commented that they had similar symptoms and it was also the prop shaft...

its a 2014 car with the Mazda box, BMW/titan LSD and has the grease nipples on the prop. 

Will report back once I get the wheels back tomorrow 


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Lots of good advice on offer. I would start by checking whether the tyres are truly round, as out-of-roundness will produce exactly the symptoms you describe. Can you swap front and rear wheels and re-test? Mind you, 100+ on the public highway could pose a problem.


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"I would have thought that if it was propshaft it would be noticeable in lower gears at high revs. It would not necessarily be road speed related ..."

Why's that?  The prop increases speed in direct proportion to road speed.  

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Good news, it would appear that the vibration is related to the tyres

The wheel balance was way off and one of the tyres is certainly not quite round!

Fortunately I have a new set ready to be fitted next week. Hopefully the next track day will be vibration free!

Thanks for all the advice and comments.

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Back to the top with this one...

whilst the old tyres were not quite round the vibration does not seem to be related to them. New tyres are on and its still there.

I had excessive play in the radius arm bushes  which I have replaced but were not the culprit either.

I think the vibration is worse when things are warmer/hot. Would this be indicative of wheel bearings? There is no play in the rear wheels or any rough feeling when turning by hand.


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Are the rear wheels the same width front and rear. If so could you swap front to rear and try to see if there is a change. I have had a prop shaft joint that was only showing that it was worn in a particular place as it was turned.

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I had ruled out the wheels/tyres. I had a spare set of tyres that I had mounted and balanced and swapped front to back in separate tests and the results were the same. However, did not realise there could be an issue with the Apollo wheels also. How could I check that?

I made a video of the potential play in the propshaft, do you think this is ok?



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The Elephant in the room is the LSD - the only component left to come under suspicion.

Unusual for vibration from an LSD at the speed suggested but for some reason the internals may not like the rotation speed at the speed suggested.

From high speed is there any harsh vibration or noise on deceleration especially with the right foot off the accelerator on over run?

If after extensive trouble shooting the vibration is still there the only alternative is to remove the LSD for an internal check.

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The rotating plates in the LSD have minimal mass an under load would be clamped up - you'd be unlikely to replicate the same orientation every time, unless there are any other noises from the Titan which could indicate snapped bellevilles then I would look elsewhere.

Have you checked the driveshafts an cv joints....?

When you looked at the prop did you see any faint signs of spot welds on the tube that could indicate where a balance plate has come adrift...?

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